FRZB and glaucoma: The implication of cytokines in glaucoma was further explored by determining the levels of TGF-β2 and secreted frizzled-related protein 1 (SFRP1) in the aqueous humor obtained from 126 eyes with different types of glaucoma (POAG, CACG, primary angle-closure suspects (PACS), and AACG), via conventional ELISA.